A cantilever-type screen printing machine is one of many important printing machines and is particularly suitable for precision printing on circuit boards. This type of screen printing machine typically includes a platform having an upper surface defining a printing bed, an elevating slide base provided to one lateral side of the platform, a transverse slide base mounted on the elevating slide base to move leftward and rightward, a cantilevered printing head including a scraper and an ink reclaiming blade forward extended from the transverse slide base and adapted to slide leftward and rightward, a cantilevered arm forward extended from each lateral side of the transverse slide base, and a clamping support provided at a lower side of each of the two cantilevered arms for holding a screen plate between the two cantilevered arms. When an object to be printed is positioned on the printing bed, the printing head is pneumatically or electrically driven to transversely move and scrape ink on the screen plate. At this point, the printing head produces a downward pressure, causing the ink to penetrate through the screen plate to the object to be printed and create a printing effect via patterns on the screen plate.
Currently, there are many different types of screen printing machines available in the market, including cantilever type, four-pillar type, electric type, electric vertical type, pneumatic type, etc. All these types of screen printing machines have generally the same printing head structure. When the screen printing machine operates, printing ink remained on the scraper of the printing head tends to drip down to the screen plate in the course of ink reclaiming, and would very possibly fall on are as of the screen plate that have not been scraped by the ink reclaiming blade to overflow into the printed object to result in uneven thickness or diffusion of the printing ink on the object and therefore adversely affect the printing accuracy and quality.
Moreover, in the conventional screen printing machine, it is impossible to reclaim some types of expensive printing ink, such as silver paste and magnetic induction ink, when the printing is completed. The expensive ink remains at peripheral are as of the screen plate and is unnecessarily wasted. There are also some special ink or screen plates that would cause overflow of ink below the screen plate in the course of reclaiming ink to adversely affect the printing quality.
In brief, in the conventional screen printing machine, there is not proper way for handling the ink residue in the course of ink reclaiming. The ink residue is allowed to overflow to the printed object, causing uneven thickness of ink on the printed object and poor printing quality. The expensive ink residue on the screen plate without being reclaimed forms an unnecessary waste in the printing. Moreover, the ink residue exposed to ambient environment over a prolonged time tends to become dried and degraded to reduce the printing quality, too.